var cities = [
    {
        id: 1,
        name: '北京',
        schools: [
            {
                id: 1,
                name: '北京大学'
            }, {
                id: 2,
                name: '清华大学'
            }
        ]
    }, {
        id: 2,
        name: '上海',
        schools: [
            {
                id: 1,
                name: '上海师大'
            }
        ]
    },
    {
        id: 3,
        name: '天津',
        schools: [
            {
                id: 1,
                name: '天津大学'
            }, {
                id: 2,
                name: '南开大学'
            }
        ]
    },
]